During the winding and unwinding of a web material, paper in particular, problems can arise as a result of the deflection of the winding roller depending upon the relationship of the winding mass, web width, physical properties of the winding layers (for example, the winding hardness, extension, compression, and frictional behavior of the paper), the stiffness and the bearing spacing of the winding shaft and of the reel spool.
Problems can also arise, especially when a contact or feed roller is being used, which is pressed substantially horizontally against the winding (i.e. roll) on the winding roller. The differing deflections of the feed roller and the winding roller which result, lead to a non-uniform contact pressure curve across the width of the web. This further results in folds and breaks which occur along the edges of the winding.
From German unexamined laid open patent application DE 36 39 244 A1, it is known that a differential deflection can be compensated for by means of a complete or partial lifting of the weight of the roller by means of supporting belts.
In the case of the winding device described above and known from German unexamined laid open patent application DE 40 26 597 A1, there is created an over-pressure that forms an air cushion in the space between the winding roller and the support rollers, wherein the support rollers are placed parallel to the axis of the winding roller.
However, both prior art devices do not go easy on the winding surface, since both the support rollers as well as the supporting belt exert a mechanical influence on the web being processed, and specifically, at the winding device with the air cushion space, as the sealing at the two axial ends of the air cushion space is difficult to maintain because of the changing winding radius which, for example, can increase from 500 mm to 3000 mm.
From German unexamined laid open patent application DE 42 01 815 A1 (FIG. 7), it is known that underneath the winding roller and extending throughout its length, a compression chamber is positioned which is open at the top and acted upon by compressed air, and which is vertically adjustable and can be swiveled. The compression chamber is provided at its front upper edge with sealing strips adaptable to the curvature of the winding roller by means of adjusting elements placed inside the compression chamber, and at its one longitudinal upper edge also with a sealing strip, and at the other longitudinal upper edge with a spacer roller that extends along this upper edge. The sealing strips are held at a distance from the winding roller, the distance corresponding to a desired air gap, by means of a spacer roller that lies against the winding roller during the swiveling of the compression chamber against the winding roller, in order to prevent any friction between the winding roller and the sealing strips. Referring to FIG. 8, an additional spacer roller is supported along the other longitudinal upper edge of the compression chamber. This system has significant disadvantages due to its numerous components. For example, such an arrangement is expensive and does not operate in a non-contacting manner which could damage the web.